Temperature measurement in nuclear magnetic resonance has traditionally been accomplished by thermocouple replacement or by the measurement of a temperature-dependent frequency difference between two nuclear resonances. If the two nuclei being used for thermometric measurement are the same isotope as the nuclei being observed, they appear superimposed on the observed spectrum unless measurement is accomplished by tube replacement. This superimposition often obscures the observed spectrum, especially in the narrow shift range of .sup.1 H nuclei. Alternately observing one isotope and then another for temperature determinations solves this problem. However, most nuclear magnetic resonance (NMR) spectrometers are capable of observing only one isotope at a time. Thus, temperature determination simultaneous to spectral acquisition is ordinarily still not possible.